In this article, I concentrated on the demise of the South Tower. I had read what was said about this collapse in the work of the National Institute of Standards and Technology—the only serious attempt by a government agency to explain the collapses of WTC 1, 2 and 7—and I was unsatisfied. I was convinced that NIST’s claim that the recorded seismic signals were caused by debris striking the earth—was wrong, and because it was wrong it hid the possibility that explosions contributed to the collapses.

This is a long and ambitious article, but in my view the main conclusions are solid. Indeed, I probably conceded too much to the official hypothesis: it is quite possible that the debris impact had nothing at all to do with the recorded seismic signals.